Telescoping antenna -- why is there a knob on top?

  • #1
19
2
Summary:
Does the knob at the end of a telescopic antenna have a significance?
This is probably a trivial or even a stupid question, the reason I am writing here is I couldn't find something satisfactory online. I am a new amateur radio operator. Currently enjoying listening to SW and MW bands. I have a nice radio receiver with a long telescopic antenna. I have noticed that the knobs at the end of telescopic antennas sometimes come in different sizes. Are they there only for ease of handling when increasing the length of antenna or preventing the end from slipping inside? Or do they have a significance in terms of some technical detail like introducing a capacitive load or so?
 

Answers and Replies

  • #2
Baluncore
Science Advisor
9,148
3,681
They are there to protect your eyes.
 
  • Like
  • Informative
Likes rude man, Spinnor and Keith_McClary
  • #3
davenn
Science Advisor
Gold Member
9,504
8,519
Summary:: Does the knob at the end of a telescopic antenna have a significance?

Are they there only for ease of handling when increasing the length of antenna or preventing the end from slipping inside?

Both .... something easy to hold whilst extending the antenna and definitely to stop the inner tubes from disappearing inside
 
  • #4
sophiecentaur
Science Advisor
Gold Member
2020 Award
25,963
5,267
Summary:: Does the knob at the end of a telescopic antenna have a significance?

preventing the end from slipping inside?

They are there to protect your eyes.
Both, I should say. Lose the inner one down the inside and you may never get it back.
 
  • #5
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
26,942
10,750
Lose the inner one down the inside and you may never get it back.
Tweezers and needle-nose pliers. Don't ask me how I know.
 
  • Like
  • Haha
Likes berkeman, jim mcnamara, Keith_McClary and 2 others
  • #6
Nugatory
Mentor
13,395
6,390
Tweezers and needle-nose pliers. Don't ask me how I know.
It is also easier if you apply copious and creative swearing before you start in with the grasping tools.
 
  • Like
  • Haha
Likes davenn and sophiecentaur
  • #7
1
1
They were there long before the antenna became telescoping. Static dissipation. all the rest of the answers are also valid, but, now you know it's a there for a real function to the radio. A point would allow rapid discharge rather than slow bleed off. That rapid discharge would equate to noise and audio bursts inside the the radio.
 
  • Like
Likes alantheastronomer
  • #8
Baluncore
Science Advisor
9,148
3,681
They were there long before the antenna became telescoping.
A ball or a capacity hat on a vertical whip transmitting antenna reduces corona discharge noise. The capacity hat also reduces the length of whip antenna needed for resonance.

The OP specifically referred to a radio receiver with a telescopic antenna. Static discharge is not a problem on receive because the antenna should be deliberately grounded through the front end of the receiver.
 

Related Threads on Telescoping antenna -- why is there a knob on top?

  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
3
Views
5K
  • Last Post
Replies
8
Views
30K
  • Last Post
Replies
9
Views
7K
  • Last Post
Replies
2
Views
672
  • Last Post
Replies
8
Views
919
  • Last Post
Replies
3
Views
4K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
15
Views
6K
  • Last Post
Replies
19
Views
18K
Top